Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$117.62	5.365%	$123.9303	$123.93	$123.95	$123.90
Purchase #2	$12.89	12.811%	$14.5413	$14.54	$14.55	$14.50
Purchase #3	$100.89	9.548%	$110.523	$110.52	$110.50	$110.50
Purchase #4	$172.80	12.160%	$193.8125	$193.81	$193.80	$193.80
Purchase #5	$73.35	12.839%	$82.7674	$82.77	$82.75	$82.80
Purchase #6	$207.73	3.496%	$214.9922	$214.99	$215.00	$215.00
Purchase #7	$91.28	8.549%	$99.0835	$99.08	$99.10	$99.10
7 purchase totals =	$776.56		$839.6502	$839.64	$839.65	$839.60